According to the current state of the art, hyperglycaemia and associated causes and sequelae (including diabetes mellitus) are treated by the administration of insulin (e.g. material isolated from bovine pancreas or obtained by genetic engineering techniques) to the diseased organisms in various forms of administration. All methods known hitherto, including more modern procedures, are distinguished by the requirement of a large amount of material, by high costs and often by a distinct impairment of the quality of life of the patients. The conventional method (daily i.v. insulin injection, customary since the 1930s) treats the acute symptoms of the disease, but after prolonged use leads inter alia to serious vascular changes (arteriosclerosis) and nerve damage.
More recently the installation of subcutaneous depot implants (the insulin is released in metered amounts, and daily injections are unnecessary) and implantation (transplantation) of intact Langerhan""s cells into the functionally impaired pancreatic gland or into other organs and tissues have been proposed. Such transplants require a high level of technical resources. Furthermore, they involve a surgical intervention into the recipient organism, which is associated with risks, and even in the case of cell transplants require methods of suppressing or circumventing the immune system.
The use of alanyl pyrrolidide and isoleucyl thiazolidide as inhibitors of DP IV or of DP IV-analogous enzyme activity is already known from PCT/DE 97/00820 and the use of isoleucyl pyrrolidide and isoleucyl thiazolidide hydrochloride is already known from DD 296 075. Isoleucyl thiazolidide, which is used in the latter prior art, is a natural, that is to say L-threo-isoleucyl thiazolidide: on the priority date and also on the application date of the two specifications, only that form, the natural form, of isoleucyl thiazolidide was available.
It has been established that those compounds, especially L-threo-isoleucyl thiazolidide, are good effectors for DP IV and DP IV-analogous enzyme activities, but the use of that compound may give rise to certain problems in the case of some patients or some forms of the disease:
Depending upon the symptoms and the severity e.g. of diabetes mellitus it would be desirable, for example, to have available effectors that have an action different from that of the known compounds: for example, it is known that diabetes mellitus patients must be xe2x80x9cstabilisedxe2x80x9d individually in order that their illness can be treated in an optimum manner. In some cases, for example, a reduction in the activity by DP IV effectors ought to be sufficient. It is also possible that too high a level of inhibitor activity and the permanent administration of the same medicament, especially in view of the life-long duration of treatment, may result in undesirable side-effects. Furthermore, it could also be desirable to improve certain transport properties in order to increase the rate of absorption of the effectors in vivo
The present invention relates to dipeptide compounds and compounds analogous to dipeptide compounds that are formed from an amino acid and a thiazolidine or pyrrolidine group, and salts thereof, referred to hereinafter as dipeptide compounds, and to the use of the compounds in the treatment of impaired glucose tolerance, glycosuria, hyperlipidaemia, metabolic acidoses, diabetes mellitus, diabetic neuropathy and nephropathy and also of sequelae of diabetes mellitus in mammals.
The invention therefore relates also to a simple method of lowering the blood sugar concentration in mammals with the aid of dipeptide compounds as activity-reducing effectors (substrates, pseudosubstrates, inhibitors, binding proteins, antibodies etc.) for enzymes having activity comparable to or identical to the enzymatic activity of the enzyme dipeptidyl peptidase IV.
DP IV or DP IV-analogous activity (for example the cytosolic DP II has a substrate specificity almost identical to DP IV) occurs in the blood circulation where it splits off dipeptides highly specifically from the N-terminus of biologically active peptides when proline or alanine are the adjacent residues of the N-terminal amino acid in their sequence.
The glucose-dependent insulinotropic polypeptides: gastric inhibitory polypeptide 1-2 (GIPI1-42) and glucagonlike peptide amide-1 7-36 (GLP-17-36), that is to say hormones that stimulate glucose-induced secretion of insulin by the pancreas (also called incretins), are substrates of DP IV, since the latter is able to split off the dipeptides tyrosinyl-alanine and histidylalanine, respectively, from the N-terminal sequences of those peptides in vitro and in vivo.
The reduction of such DP IV and DP IV-analogous enzyme activity of the cleavage of those substrates in vivo can be used to bring about effective suppression of undesired enzyme activity under laboratory conditions and also in the case of pathological conditions in mammalian organisms. For example, diabetes mellitus Type II (including adult-onset diabetes) is based on a reduced secretion of insulin or disorders in the receptor function resulting inter alia from anomalous incretin concentrations arising from proteolysis.
The aim of the invention is therefore to provide new (especially activity-reducing) effectors for the treatment of e.g. impaired glucose tolerance, glycosuria, hyperlipidaemia, metabolic acidoses, diabetes mellitus, diabetic neuropathy and nephropathy and also of sequelae of diabetes mellitus in mammals, and a simple method of treating such diseases.
This aim is achieved according to the invention by the provision of dipeptide compounds or analogues of dipeptides that are formed from an amino acid and a thiazolidine or pyrrolidine group, and salts thereof.